The hollow-body knee tuck is a bodyweight abdominal exercise performed on the floor. It is similar to both the hollow-body hold and the knee tuck or reverse crunch, combining elements of both. It primarily targets the muscles of the rectus abdominis, or “six-pack” muscles. It can be performed for reps or time, either as part of an ab-focused workout or as a component of a circuit workout.
Combines isometric and dynamic abdominal training
Targets the six-pack muscles, but also the obliques and hip flexors
Great for variety if you've been doing standard hollow-body holds or knee tucks